W. Fernando

Modulator based high bandwidth optical readout for HEP detectors

Optical links will be an integral part of future LHC experiments at various scales from coupled sensors to off-detector communication. We are investigating CW lasers and light modulators as an alternative to VCSELs. Light modulators are small, use less power, have high bandwidth, are reliable, have low bit error rates and are very rad-hard. We present the quality of the links at 10Gbps and the results of radiation hardness measurements for the modulators built based on LiNbO3, InP, and Si. Also we present results on modulator-based free space data links, steered by MEMS mirrors and optical feedback paths for the control loop.

Development of low mass optical readout for high data bandwidth systems

At Argonne National Laboratory the High Energy Physics and Center for Nanoscale Materials Divisions are working on a project to develop a new generation of detector readout using high speed data transfer optical devices that can be implemented in particle physics or for long distances. Free-space communications devices offer the potential for reductions in mass, power, and cost of data paths for on-board trigger and readout of tracking detectors. The project involves three areas of study: light modulation, the design and construction of MEMS optical devices, and the control systems for maintaining precise laser light positioning. We demonstrate an optical link in air over one meter and with low error rate at 1 Gb/s. We demonstrate steering of an optical beam over a meter with a precision of 5 micrometers utilizing a MEMS mirror and reflected light in the feedback loop. For early testing, light modulation tests with a fiber link using Li-Niobate modulators and a data generation and error checking chip are done at 1Gb/s. Many companies and universities are developing modulators which will be incorporated into CMOS chips. We are doing radiation hardness studies for one of the materials involved. Laser light will need to be steered on to and kept centered on the detector in the presence of thermal or mechanical motion, etc. This steering will be controlled by MEMS mirrors. Polycrystalline and crystalline silicon based mirror designs are being studied. We review the current status of the project and outline plans for the future development of the system.

STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN ARRAYS

The silicon trackers of the ATLAS experiment at LHC (CERN) use optical links for data transmission. VCSEL arrays operating at 850 nm are used to transmit optical signals while PIN arrays are used to convert the optical signals into electrical signals. We investigate the feasibility of using the devices at the Super LHC (SLHC). We irradiated VCSEL and GaAs PIN arrays from three vendors and silicon PIN arrays from one vendor. All arrays can be operated up to the SLHC dosage except the GaAs PIN arrays which have very low responsivities after irradiation and hence are probably not suitable for the SLHC application.